A week after Web hosting company Network Solutions LLC dealt with a large-scale infection of WordPress-driven blogs, the company acknowledged that other sites it hosts have been compromised.

"We have received reports that Network Solutions customers are seeing malicious code added to their websites, and we are really sorry for this experience," said company spokesman Shashi Bellamkonda in a Sunday blog post. "At this time, since anything we say in public may help the perpetrators, we are unable to provide details."

On Monday, another Network Solutions spokesperson declined to get more specific or answer questions, including queries about what moves the company was making and how many sites had been affected. "At this time, we believe this is affecting a subset of our hosting customers," said Susan Wade, director of corporate communications at Network Solutions. "For now, it's difficult to make a conclusive statement or provide more details publicly."

Yesterday, Securi Security Labs said that at least 50 sites hosted by Networks Solutions had been hacked and that malicious JavaScript injected into those sites was redirecting unsuspecting users to a Ukrainian attack server. The same server was involved in the earlier attacks against Network Solutions-hosted blogs.

According to the StopMalvertising blog, the attacks planted a rogue IFRAME on the hacked sites to shunt users to the attack server. That server then launches multiple exploits, including an attack kit of ActiveX exploits and three more that take advantage of Adobe Reader vulnerabilities, against visiting PCs.

Several browsers, including Microsoft's Internet Explorer 8, Google's Chrome and Mozilla's Firefox, display warnings when users are redirected to the attack site. "This web page ... has been reported as an attack page and has been blocked based on your security preferences," Firefox reports in its warning.

Firefox is one of several browsers that display warnings to users who are steered to the Ukrainian attack server.

Network Solutions had characterized the earlier attacks targeting WordPress-crafted blogs as a file permissions issue, and it initially seemed to blame users' weak passwords for the attacks. Although the company never disclosed how the blogs were hacked, it said it had addressed what it called the "root cause" by April 11.

Yesterday, Bellamkonda hinted that the newest attacks were conducted differently than those against WordPress blogs hosted by his company. "It may not be accurate to categorize this as a single issue such as 'file permissions,'" he said. He also said that passwords were "not related to this issue."

Network Solutions declined to say today whether it had figured out how the second wave of attacks was carried out. "Our teams continue to work around the clock to combat this threat to us and our customers. We are also continuing to actively investigate the issue," said Wade.